1. Field of the Invention
The present invention relates to a voltage controller which controls a voltage of electric power generated from a rotational force in an alternator mounted in a passenger car, a truck or the like.
2. Description of Related Art
A conventional voltage controller used in an alternator for a vehicle has a circuit substrate, a heat radiating fin, and a casing. The fin is adhered to the substrate with a high thermal conductive adhesive. The controller is fixed to a frame of the alternator through a male type connector integrally formed with the casing. Integrated circuit (IC) chips for control circuits, transistors and the like are disposed on the substrate, and heat generated in the chips is transmitted to the fin through the adhesive and is transferred to a cooling wind.
A shape of the fin is designed while considering circumferential conditions of the controller in its operation and flow conditions of the cooling wind. Various shapes of heat radiating fins are, for example, disclosed in Published Japanese Patent First Publications No. H08-85402, No. 2000-83358 and No. 2003-244913.
FIG. 1 is a perspective side view showing a heat radiating fin representing fins disclosed in the Publications. FIG. 2 is a view showing flow directions of a cooling wind colliding with the fin shown in FIG. 1. As shown in FIG. 1, a fin 270 has a plurality of rib-like protrusions 260 disposed at predetermined intervals, and each protrusion 260 stands on a base 265 along a standing direction. A groove is formed on the base 265 between adjacent protrusions 260 in each pair. As shown in FIG. 2, when a cooling wind 280 flows toward the fin 270 in parallel to the standing direction, the wind collides with the fin 270, turns its flow direction and passes through the grooves. Therefore, each groove acts as a wind path, and heat transmitted to the fin 270 is transferred to the wind.
However, because an alternator having a heat radiating fin is mounted in a vehicle, a cooling wind inevitably includes foreign matters such as dust, mud and the like, during the running of the vehicle. Therefore, there is high probability that the foreign matters are packed or deposited in the wind path so as to prevent the wind from passing through the wind path. In this case, a cooling performance in the fin considerably deteriorates, so that the chips are sometimes over-heated and broken. Further, when the fin is manufactured, a complicated work is required to form rib-like protrusions on a fin base. Therefore, it is difficult to manufacture the fin 270 at low cost.